netdev - Re: [PATCH v3] filter: Optimize instruction revalidation code.

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]

Date:	Wed, 17 Nov 2010 10:01:56 +0100
From:	Hagen Paul Pfeifer <hagen@...u.net>
To:	Tetsuo Handa <penguin-kernel@...ove.SAKURA.ne.jp>
Cc:	<eric.dumazet@...il.com>, <mjt@....msk.ru>, <davem@...emloft.net>,
	<drosenberg@...curity.com>, <xiaosuo@...il.com>,
	<netdev@...r.kernel.org>
Subject: Re: [PATCH v3] filter: Optimize instruction revalidation code.

On Wed, 17 Nov 2010 17:06:10 +0900, Tetsuo Handawrote:

> If compilers can generate better code for continuous case values
> than discontinuous case values, then keeping BPF_S_* makes sense.

Yes, this is crucial. A compiler cannot generate a jump table of O(1) for
dense labels. The BPF_S_* translation was done to convert to a dense label
construct. So this "optimization" is a no-go.

Look at the log and read my comment for a detailed explanation.

Anyway: "code--" increments the _copied_ value, not the value in the
evaluated opcode itself. I will validate the patch!

Hagen
--
To unsubscribe from this list: send the line "unsubscribe netdev" in
the body of a message to majordomo@...r.kernel.org
More majordomo info at  http://vger.kernel.org/majordomo-info.html